1. Field of the Invention
The present invention relates generally to mobile electronics, and more particularly, to a navigation system capable of displaying a chart or map such that the area in close proximity to an area of interest is in greater scale than an area that is distant.
2. Description of the Background Art
Various types of navigation systems and methods which have been applied to route guidance systems of boats, vehicles and airplanes on water, land, or in the air or to portable navigating apparatuses and methods have been used and are well known in the art.
A common shortcoming of these systems is that the screen on which maps or charts are displayed only display either short-term planning information by zooming in on a specific location or long-term route/chart planning information by zooming out and viewing a greater area. Thus, in prior navigation systems, to view a “big picture” of a route, the user must zoom out, losing important details about the area immediately surrounding the user. This is shown in FIGS. 1 and 2 (long term) and FIGS. 4 and 5 (short term). In addition, because nautical charts tend to be quite large, and computer screens tend to be quite small, it is often difficult to determine where you are on a chart because only a small portion of the chart can be viewed on any usable scale. These same difficulties are present in other map and chart types.
Historically, the “big picture” view is generated by zooming out (viewing the same chart at a reduced level of zoom) or loading a chart of a smaller scale (displaying a chart which covers a wider area), as shown in FIGS. 1 and 2. When a chart is zoomed out, the user is able to view more of the chart, but the details become increasingly difficult to read. Important navigational information can become so difficult to read that it is virtually useless. Further, when loading charts of smaller scale, details that are important for short term navigation are often left out of small scale charts in order to reduce the general clutter of the chart while attempting to show those features that are considered most important at that scale.
On a traditional electronic chart, if an object is 100 pixels from the user on the chart and 1 mile from the user in reality, then an object 200 pixels from the user on the chart will be approximately 2 miles from the user in reality. This function of distance from the user on a chart to distance from the user in the real world is linear (or it at least matches the chart projection), and can be represented as follows:    Linear    100 pixels=1 mile    200 pixels=2 miles    300 pixels=3 miles    400 pixels=4 miles